The invention relates to a device for temporarily storing preferably unlacquered cans that are preferably made of metal, comprising a supplying conveyor system, an intermediate storage system (for the cans), and a handling system which is designed and controlled for simultaneously transferring a plurality of cans from the conveyor system into the intermediate storage system.
Up to now, as an intermediate storage for temporarily storing unlacquered cans between individual production steps in a can production plant, so-called chain storages 100 are used which are exemplary illustrated in FIG. 8. The cans are transported from a non-illustrated production machine via a first transport chain 101 with chain pins to a chain storage 100 and are transferred into the latter via two vacuum loading drums 102, 103 that interact with each other. The loading drums are configured with push prisms, wherein each push prism holds in each case one can through suction on the circumference of the respective loading drum. Through this push function, the can held through low pressure can be removed from the transport chain 101, can be transferred to the loading drum 103 and can be pushed by latter onto the synchronously running chain storage 100.
The chain storage 100 is equipped with a multiplicity of carriages 104. The effective chain length of the chain storage and thus the stored length of cans is adjusted or controlled through the height position of the carriages 104. The transfer of the cans from the chain storage 100 to a second outfeeding transport chain 105 takes place via two further loading drums 106, 107 which work in a running direction opposite to the loaded loading drums 102, 103.
The storage capacity of known chain storages 100 is limited by the ceiling height which, in practice, is maximally 6 m. Thus, a chain storage with a length of 6 m has a storage capacity of only approximately 2,800 cans which, at a production speed of approximately 200 cans/min, corresponds to a storage time of approximately 14 min. In order to be able to achieve higher production outputs, efforts are made to implement higher quantities of stored cans.
Known chain storages are not only limited in terms of their storage capacity. There is also the problem that in practice the function of closing gaps is technologically manageable only up to approximately 250 cans/min. Higher speeds generate tumbling and pushing movements during the transfer by means of the loading drums 102, 103, 105, 106.
An intermediate storage system that is improved with respect to increased storage capacity is described in EP 2 192 061 A2. In contrast to a chain storage, the known storage system does not comprise a revolving transport chain with chain pins, but comprises instead transport belts on which the cans are placed so that the cans can be picked up from the supplying transport band by means of a handling system by inserting transport mandrels (insertion rods) into the cans. Temporarily storing is not carried out along a moving chain, as in the case of the chain storage, but in a high-rack storage system in which the storage containers containing the cans are temporarily stored spaced apart from each other. The disadvantage of using high-rack or paternoster storage systems is the required space which is still comparatively large. With the handling system, the cans are mechanically gripped by means of insertion rods, swiveled by 180°, and are deposited directly adjoining each other in the storage container. Hereby, the storage volume in the storage container can be minimized; however, this approach is not suitable for unlacquered cans since brushed and washed metal cans in the unlacquered state occasionally interlock with each other which, in the worst case, can result in stoppage of the intermediate system or to the loss of cans. Moreover, as in the case of the chain storage, the spatial depth is not utilized with the known intermediate storage system.
Furthermore, it is a disadvantage that with the handling system of the known device, which comprises insertion rods, only limited accelerations or decelerations can be implemented because otherwise there is the risk that during the transfer of the cans from the supplying conveyor system to a separate delivering conveyor system, cans can be spun off by the mandrels gripping the cans, or can slip or tumble.
An additional disadvantage is the limited possibility of closing (individual) gaps.
Proceeding from the aforementioned prior art, it is an object of the invention to propose a device and a method for temporarily storing preferably unlacquered, in particular brushed (metal) cans, by means of which gaps can be optimally closed without affecting the overall speed of the can production plant. Preferably, in addition, the available space shall be optimally utilized for temporarily storing the cans, wherein the method and the device shall be preferably suitable for use or implementation in a can production plant by means of which more than 300 cans/min, preferably more than 400 cans/min, and more preferably more than 500 cans/min can be produced.